One of the biggest problems I've found when talking about Unicode and character encoding that it is so easy to misunderstand how encoding works. Joel Spolsky has written a decent blog on the topic broadly without requiring you to read a 600 page book. Here is Joel's blog http://www.joelonsoftware.com/articles/Unicode.html.
Additionally, several Ektron articles exist on the topic and cover some specific concepts as they relate to Ektron products.
Or you can search the Ektron Knowledge Base for "Unicode" for more articles.
When in doubt, use UTF-8 encoding. It supports all languages that can be represented by Unicode. UTF-8 is widely supported by browsers, databases and XML parsers. The Ektron CMS uses UTF-8. There should be no reason to use other older encodings such as Shift-JIS or ISO-8859.